Yep, but -if you're not using an unique ring- the difference is bigger since you usually have 50-60+ life flat on rings. Besides, it gives 49% to 63% chaos res that in some situation could be better than 300-400life, and gives you all the chaos res you need (almost).

First of all, phys reduction is different than ele reduction.
phys reduction doesnt work (good) with larger hits, and your problem IS big hits :) . Here's how armour works http://pathofexile.gamepedia.com/Armour

Furthermore, 10% ele resist is HUGE, I'll explain with an example.

with 80% res, from a hit with base damage 100, you'll take 20damage.

with 90% res, you'll take 10damage.

The effectiveness is 50% less damage (20 -> 10)

These two things makes topaz a better choice over granite. On my LightCoil AA char i had 1topaz and 1granite btw ;)

2) you have low crit multi since you've not a crit dmg support on 5L. With low attack speed this should down a lot your dps

3) seems fine for a non-crit build.

My hints:
it's hard to do a cheap ele crit, since you need

6L -> ST + LMP + LGoH + Blood Magic + WED + crit dmg

or

a build based on Eldritch Battery and Arctic Armour, which will give you the opportunity to take off BM gem in favor of crit dmg. This choice need more points spent for auras, leveled gems and a very good gear since you've not ES on shield. (You'll drop dodge ofc in this case, block + AA is pretty good tho)